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Comet ISON live blog

Posted by Emily Lakdawalla and Bruce Betts

05-12-2013 10:00 CST

Topics: pretty pictures, comets, explaining science, solar observing spacecraft

Comet ISON reached perihelion at 18:25 UT (10:25 PT). It's was an event that's was watched around the world, accompanied by tons of commentary and streams of photos. We updated this blog entry periodically with links to all the resources that we hear of for following the comet's progress.

Update: Comet ISON is at least mostly dead.  Most think all that remains is a rapidly fading and dispersing cloud of dust.  For insights on what happened, check below and the links therein, and read Bruce's Comet ISON wrap up blog (A Tail of Cat-Possums and the Undead), and check out Emily's animations page that includes animations of images from many different solar observation spacecraft, as well as seeing the animations below, and check our Comets page that will list all recent Planetary Society posts on comets, ISON or otherwise.

Had enough animations yet? Here's one from the STEREO Behind spacecraft, a unique perspective on the comet rounding the Sun. I (Emily) am not sure why it's so much brighter in this view than in the SOHO ones -- I suspect that the viewing geometry makes dust much more visible than from other points of view. 

ISON rounds the Sun as seen from STEREO-B (Nov 28-29, 2013)

NASA / STEREO / Emily Lakdawalla

ISON rounds the Sun as seen from STEREO-B (Nov 28-29, 2013)
This animation contains 96 images captured by the STEREO Behind spacecraft between November 28 at 00:08 and November 29 at 08:39 UTC.

Here's a really nice video put together by Babak Tafreshi that combines the SOHO LASCO C2 and C3 images:

NASA / ESA / SOHO / Babak Tafreshi

Comet ISON Dives Toward the Sun (SOHO LASCO images)
Comet ISON (C/2012 S1) captured by the SOHO spacecraft as it dives in to the sun's corona on November 28, 2013, and in a dramatic action a fraction of the icy body returns from the hell the next day. I edited this stunning sequence of images released by SOHO (Solar and Heliospheric Observatory), leveled, enlarged and sharpened them for full HD viewing.

Here is an animation from SOHO's higher-resolution camera, showing the comet fading out as it approaches perihelion; apparently some of it survived, but it's not obvious at the moment (23:30 UT on November 28) if there is an intact nucleus. Karl Battams, going out on a limb at 02:46 on November 29, thinks it might.

ISON rounds the Sun as seen from SOHO LASCO C2 (Nov 28-29, 2013)

NASA / ESA / SOHO / Emily Lakdawalla

ISON rounds the Sun as seen from SOHO LASCO C2 (Nov 28-29, 2013)
This animation contains 88 images captured by the SOHO spacecraft from November 28 at 00:22 to November 29 at 00:13 UTC.

Here is the latest LASCO C3 animation of the departure (up to date as of Nov 28 at 06:30 UT, including data through 00:18 UT). There is one more frame from much later (05:30 UT) that I have not yet added into the animation:

ISON departs the Sun as seen from SOHO LASCO C3 (Nov 28-29, 2013)

NASA / ESA / SOHO / Emily Lakdawalla

ISON departs the Sun as seen from SOHO LASCO C3 (Nov 28-29, 2013)
This animation contains 14 images captured by the SOHO spacecraft between November 28 at 20:07 UT and November 29 at 00:18 UT.

Here is the latest LASCO C3 animation of the approach (up to date as of Nov 28 at 06:30 UT, including data through 00:18 UT):

ISON approaches the Sun as seen from SOHO LASCO C3 (Nov 28-29, 2013)

NASA / ESA / SOHO / Emily Lakdawalla

ISON approaches the Sun as seen from SOHO LASCO C3 (Nov 28-29, 2013)
This animation contains 153 images captured by the SOHO spacecraft between November 26 at 21:20 UT and November 29 at 00:18 UT.

Here is the latest STEREO-Ahead animation (up to date as of Nov 28 at 18:00 UT, including data through Nov 27 10:49 UT). This version has been aligned on the comet to show its dramatic brightening:

ISON approaches the Sun as seen from STEREO-A (Nov 21-28, 2013)

NASA / STEREO / Emily Lakdawalla

ISON approaches the Sun as seen from STEREO-A (Nov 21-28, 2013)
This animation contains 264 images captured by the STEREO Ahead spacecraft between November 20 at 14:05 and November 28 at 1:29 UTC. The two vertical lines that cross the image are pixel bleeding from two bright planets (Mercury and Earth), both out of the frame. The smaller comet that appears to cross ISON's path is Encke. As ISON gets very close to the Sun it gets so bright that it saturates the detector, blooming into vertical stripes. Those aren't real; they represent charge spilling over into adjacent pixels from the too-bright comet.

Brief summary of the comet's behavior:

Websites and twitter feeds with reliable, updated information and photos:

Press briefings, Google+ hangouts, and other live events:

Expected timeline of ISON's appearance to different spacecraft cameras (all times UT) (copied from this tweet by Karl Battams):

  • Oct 10: Enters STEREO/SECCHI HI-2A (to Nov 22)
  • Nov 21: Enters STEREO/SECCHI HI-1A (to Nov 28)
  • Nov 26 0400: Enters STEREO/SECCHI COR-2B
  • Nov 27 0200: Enters SOHO/LASCO C3
  • Nov 28 0400: Enters STEREO/SECCHI COR-2A
  • Nov 28 1300-2300: Transits SOHO/LASCO C2
  • Nov 28 1600-2300: Transits STEREO/SECCHI COR-1B
  • Nov 28 1700-2200: Transits STEREO/SECCHI COR-1A
  • Nov 28 1720-1920: Transits SOHO/SUMER
  • Nov 28 1810-2010: Transits STEREO/SECCHI EUVI-B
  • Nov 28 1820ish: Transits SDO/AIA
  • Nov 29 1400: Exits STEREO/SECCHI COR-2A
  • Nov 29 2000: Exits STEREO/SECCI COR-2B
  • Nov 30 2300: Exits SOHO/LASCO C3
  • Nov 31 0000: Enters STEREO/SECCHI HI-1A (to Dec 7)
Here is an animation composed of data taken by the STEREO Ahead spacecraft through November 26 at 12:49 UT (4:49 PT):

NASA / STEREO / animation by Emily Lakdawalla

ISON approaches the Sun as seen from STEREO-A (Nov 21-26, 2013)
This animation is composed of 208 images captured over a period of five days from November 21 to November 26 as comet ISON approached the Sun. Also in the frame are Mercury, Earth, and comet Encke.

How close will ISON get to the Sun?  This close:

Comet ISON closest approach distance relative to the size of the Sun

NASA / Bruce Betts

Comet ISON closest approach distance relative to the size of the Sun
Comet ISON (C/2012 S1) approaches the Sun on Nov. 28, 2013 at a distance closer than one solar diameter away from the Sun's surface, as depicted in this diagram.

Need background/basics on Comet ISON?  Watch this 3 minute video:

Comet ISON: Super Bright or Super Lame?

Video by Planetary Society Director of Projects Bruce Betts providing the basics about Comet ISON (C/2012 S1) including information about visibility and its close pass by the Sun.

 
See other posts from December 2013

 

Or read more blog entries about: pretty pictures, comets, explaining science, solar observing spacecraft

Comments:

GET: 11/27/2013 08:56 CST

What is the other moving object (not ISON) in theStereo Ahead Heliospheric Imager video? Can be seen at 0:14/0:23 in??

stone: 11/27/2013 09:32 CST

http://soho.esac.esa.int/cgi-bin/soho_movie_theater If you select LASCO C3 and 20 images. Already shows a comet.

hosehead78: 11/27/2013 11:13 CST

@GET - I believe that is Coment Encke. http://www.planetary.org/blogs/guest-blogs/2013/1122-ison-encke-mercury-and-home.html

stone: 11/27/2013 12:01 CST

Hermann Böhnhardt told me it is ISON

Emily Lakdawalla: 11/27/2013 05:11 CST

@GET, yes that is Encke, the other small comet in the STEREO animation. @stone yes, that is ISON in LASCO C3.

morganism: 11/28/2013 10:29 CST

That orbit is significantly different from the plotted parabola. http://soho.esac.esa.int/hotshots/index.html/ISON_LASCO1.jpg Hope it didn't change the plane elliptic too.....

Andrew Planet: 11/29/2013 05:53 CST

If we landed a functional spacecraft on comet which the ability to send back data, could it take us much further than the Voyagers in less time and then detach itself again when it has? We'd save on fuel at least.

speakertoanimals: 11/29/2013 08:04 CST

Hard to credit why professional astronomers are surprised by ISON as comet Lovejoy did almost exactly the same thing almost exactly two years ago. ISON is bigger and thus has a chance not to break up as did Lovejoy. I'm getting tired of all the hype by people who are PAID to know better.

Behnam: 11/30/2013 02:43 CST

Here is my opinion about what happens to ISON: Here there are three major velocities in play drift velocity Vdrft & diffusion velocity Vdif. & Scape velocity. The average drift velocity of ISON should be calculated using conservation of Energy. That is = SQRT(Integral [From= its staring rest position in space or say infinite, to closest point to Sun] of { 2.G(gravitational constant).M(mass of Sun)/R^2(distance from the Sun)} dr) Then, one can calculate the scape velocity at the closest point ISON comes to the Sun, as well. IF Scape Velocity is greater than then the ISON gets captured by the sun; otherwise, ISON scapes. To account for the effect of Vdif as results of heating of ISON gases, the gases in ISON would have velocities ranging from - to + . Therefore, all the gas particles with velocity less than Vscape would be captured by the sun, and all the gas particles with speed more than Vscape will scape. So we should see a tail ahead of ball, instead of ball a head of tail, coming out of the sun. What gas particles would be, I think majority of molecules ionize to nucleus & electrons so it would be plasma. The scaped plasma gets cooled at some point in future, if it does not hit a planet or other object, and forms the ISON again.

Carl Schmidt: 12/01/2013 05:12 CST

Still preliminary, but there's mounting evidence we're seeing an atomic iron tail in the integral-field Echelle data from McDonald Observatory on Nov. 20th. At .44 AU, ISON was still too cold for much iron sublimation and reactions in the coma are a more likely source.

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